I would not worry about the tiny difference in frame rate. The difference is too small to notice an infrequent frame slip. This is especially true for content that has low motion like a concert. I recommend to try editing the clips and see how you like the result. Just be sure to set the video mode to one of the frame rates: 30.00 or 29.97.
They will almost certainly not stay in sync for the duration of a 3 hours concert. Each recording device will have a slightly different clock.
I recommend that you try the Align To Reference tool.
For 3 hour clips, it might take a very long time to run. I have never test it for such long clips.